Conservation of energy

Energy is always conserved, but to find out where it has gone we sometimes need to look inside matter. Macroscopic processes can lead to microscopic changes.


Summary

Mass pushed up a frictionless slope

When work is done on a block on a slope it gains both kinetic and potential energy but when the force is removed the kinetic energy is converted to potential energy. At the top, the potential energy gained is equal to the total work that was done:

\(Fd = mgh + {1\over2}mv^2\)

Ball thrown vertically

When a ball leaves your hand it has kinetic energy. As it rises \(E_k\rightarrow E_p\).

Energy lost when bouncing

When a ball bounces some energy is lost. The energy goes to the kinetic and potential energy of the atoms.

 If the ball itself could squash, the energy could be considered to have transferred to elastic potential energy.

Mass on a spring

When a spring is stretched, work is done, so energy is transferred. This energy is stored in the spring as elastic potential energy.

\(E_p = {1\over2}kx^2\)

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